Green’s Dictionary of Slang

(US) cold; usu. in phr. it’s bloody baltic.

1997–2001		Online Sl. Dict. 🌐 baltic adj 1. cold.
2007		R. Milward Apples (2023) 112: [M]e and Ste were baltic in the rain.
2020		G. Armstrong Young Team 16: It’ dark n baltic [...] The cold nips at our fingers n toes.